The present invention is directed to combustion fuel additives and more particularly to additives for kerosene, diesel fuel, gasoline, high pressure steam boiler fuel such as No. 6 fuel, low pressure steam boiler fuel such as No. 2 or No. 4 fuel, and coal.
It is well known to combine combustion fuels with various additives in order to improve the combustion performance of the fuel. For example, H. Lamprey discloses in "Annals of the New York Academy of Science", 519 (1957) at page 22 that metal acetylacetonates catalyze combustion, prevent sludge and hard carbon deposits and act as soot-removal agents when used in lubricating and fuel oils. Similarly, Australia Patent No. 219,409 discloses at column 2 that acetylacetone compounds of iron or other transition metals of the iron group reduce smoking and carbon deposition and improve anti-knock properties of hydrocarbon fuels; see "Chemical Abstracts" 55 9856D (1961). Other metal complexes of enol forms of beta-dicarbonyl compounds are also known in fuel additive applications as well as in other applications. For example, cerium tri-1,1,1,5,5,5-hexafluoropentane-2,4-dionate and cerium tri-2,2,6,6-tetramethylheptane-3,5-dionate have been used in fuel additives.
The metal enolates of enolizable beta-dicarbonyl compounds useful in fuel additives as well as in other applications are usually metal acetylacetonates, which have the following formula: ##STR3## wherein a is the valence of the metal.
The enol forms of other beta-dicarbonyl compounds are also known as chelating agents for metals. For example, in addition to the cerium complexes shown above, benzoyl acetone and formylacetone have been used to form metal complexes. Moreover, one or both of the carbonyl groups may be part of a ring. For example, 2-ketocyclopentanecarboxylic acid esters have been used as complexing agents for metals.
In these metal complexes, it is generally thought that the metal is the more active component. The organic chelating group aids in rendering the metal soluble in the medium in which it is used.
Other ingredients besides metal enolates have also been used as combustion fuel additives. For example, picric acid and tricresyl phosphate have been used for this purpose. The formulation of combustion fuel additives, however, is more an art than a science. It is generally difficult to predict the effect of a particular additive. Thus, most additives are formulated on the basis of trial and error.
Additives have been used in a variety combustion fuels. For example, kerosene heaters have recently become increasingly popular in the United States. Additives are needed to improve the combustion performance of kerosene, to reduce the build-up of gums on the wicks of such heaters, and to reduce the amount of soot given off during their use.
Additives are also needed in motor fuels. In addition to improving the octane rating of motor fuels, it is important for an additive to be able to reduce the amount of particulates which are given off during the combustion of many motor fuels.
Additives are also needed in high pressure steam boiler fuels such as No. 6 fuel. One problem with the use of No. 6 fuel is that slag tends to condense on the tubes of high pressure steam boilers. Slag is generally thought to be a residue of the distillation process and to contain salts such as sodium silicate, sodium aluminum silicate, and various vanadate salts. The build-up of slag adds thickness to the tubes and prevents heat transfer from hot gases to the boiler tubes. In view of these problems, it is important that high pressure steam boiler fuel additives reduce slag.
In view of the increasing cost of combustion fuels and of the increasing pollution problems caused by the combusting of fuels, a need continues to exist for improved combustion fuel additives which give superior combustion performance as well as eliminate the various problems which arise during the combustion of different types of fuels in their various applications.